Snow-ice accretion and snow-cover depletion on Antarctic first-year sea-ice floes

Abstract

Between austral late winter 1993 and austral autumn 1998, during five cruises aboard the research vessel Nathaniel B. Palmer, almost 300 m of core was obtained from first-year ice floes in the Ross, Amundsen and Bellingshausen Seas. Analysis of the texture, stratigraphy and stable-isotopic composition of the ice was used to assess the magnitude of the role of flooding and snow-ice formation at the base of the snowpack in the thickening of the ice cover and the thinning of the snow cover. Snow ice occurred in all ice-thickness categories and made a significant contribution to the total ice mass (12−36%) in both autumn and winter. Although the amount of snow ice was often exceeded by the amount of frazil ice and congelation ice, the thickness of individual layers of each ice type indicated that snow ice often made a greater contribution to the thermodynamic thickening of the ice cover than the other ice types. The larger quantities of frazil ice and congelation ice were primarily the result of dynamic thickening. Flooding and snow-ice formation reduced the snow cover to 42−70% of the total snow accumulation depending on time and location. On the basis of this information, ship-based snow-depth estimates were adjusted to estimate the total snow accumulation on different ice-thickness categories.

Macro-nutrient concentrations in Antarctic pack ice: Overall patterns and overlooked processes

“…Seawater flooding is commonly observed in Southern Ocean pack ice characterized by high snow accumulation (up to 3 m) on relatively thin ice . As a result, the snow-ice interface often sinks below sea level, resulting in a negative ice freeboard (the elevation of the snow-ice interface relative to the local sea surface) and hydraulically forcing the infiltration of seawater and brine into snow, with slush and snow ice forming in the process (Jeffries et al, 1997(Jeffries et al, , 2001Haas et al, 2001;Maksym and Markus, 2008;Papadimitriou et al, 2009).…”

A 1-D modelling study of Arctic sea-ice salinity

“…The resulting frozen mix of snow and ocean water, called snow ice, can be identified by various means in ice cores, from which we know that flooding occurs mainly in the Antarctic and contributes up to 25 % of ice production in certain areas Maksym and Jeffries, 2001). We base our understanding and treatment of flooding on the work of Jeffries (2000, 2001) and Jeffries et al (2001). To readers interested in flooding we recommend the PhD thesis of .…”

Large viruses in Ross Sea late autumn pack ice habitats

“…To provide an overview of the late autumn environment, a synopsis of conditions in the study area follows; detailed analyses of ice structure are reported in Jeffries et al (2001), and abundance and biomass of organisms of ice communities will be reported elsewhere (Garrison et al unpubl., Gibson et al unpubl. ) et al unpubl.).…”

“…Snow cover ranged from 0 to 36 cm. Frazil ice predominated north of 70°S, and congelation ice predominated south of 70°S (Jeffries et al 2001). Chl a concentrations were generally higher north of 70°S, reaching a maximum of >20 mg m -2 (Garrison et al 1999).…”

“…Three sites along the transect, representative of unridged ice topographic variability, were selected for ice coring for ice physics studies (e.g. Jeffries et al 2001). If the ice physics core was visibly colored at a site, a virus core was taken there; otherwise a virus core was taken from the site closest to the ship.…”